Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Are there any GUT's that do not violate baryon number?

  1. May 11, 2007 #1
    Are there any GUT's that do not violate baryon number?

    It's my understanding SU(5), SUSY SU(5) and SO(10) have been falsified by current bounds on proton decay.

    Alternatively, given the current bounds of proton decay is 10^33 years 95% confidence and counting, if physicists a century from now of looking for proton decay and come up with null results conclude that baryon number is conserved, would this falsify all GUT scenarios?
  2. jcsd
  3. May 11, 2007 #2
    I think there have been a lot of efforts modifying exsiting models to avoid such a problem. Maybe search a little bit in the recent literature, lots of stuff would jump out. :)
  4. May 12, 2007 #3
    No, if you put leptons and quarks into the same multiplet, there will always be interactions which transform quarks into leptons.

    However, there are GUTS that do not violate present experimental bounds on baryon-number-violating interactions, e.g. proton decay. I don't think that SO(10) or susy SU(5) have been strictly ruled out.
  5. May 12, 2007 #4


    User Avatar
    Science Advisor

    SO(10) and SuSy SO(5) are most assuredly not ruled out. Its known that you can add R Symmetry in various ways to escape the bound.

    Baryon number cannot be conserved either. Strong bounds from astrophysics on matter/antimatter asymetry more or less conclusively point to some baryon violation at least in the early universe.

    Theoretically there is no good reason to expect such a thing to be conserved either, and more or less an artifact of the standard model.
    Last edited: May 12, 2007
  6. May 12, 2007 #5


    User Avatar

    You could alway do like Glennys R. Farrar and add a fifth force/particles to explain dark matter.
  7. May 12, 2007 #6
    WHat are their predicted proton half-lives and how many years before Kakimonde will reach that number?

    Do you believe in magnetic monopoles?

  8. May 12, 2007 #7
    Doesn't more recent work show that even the standard model predicts proton decay? (Although from what I understand, the half life it predicts is so long that it does not matter)
  9. May 12, 2007 #8
    I do wonder:
    how many more decades of a null result before physicists consider the possibility that baryon number is conserved. I understand that Kakimonde puts the bounds at 10^35 years. Perhaps quarks and leptons are not in the same multiplet.
  10. May 12, 2007 #9


    User Avatar
    Science Advisor

    "how many more decades of a null result before physicists consider the possibility that baryon number is conserved."

    That just can't happen until we see more antimatter in the universe.

    Its a general theorem that in order to create the sort of condition where you have the observed ratios, you need three conditions in the early universe. A healthy amount of CP violation, departure from thermal equilibrium and baryon number violation. Where the quantitative values depend on each other.

    Point being, there has to be some new physics *somewhere* where this is allowed to take place. No one knows how this works really, but if you can solve this problem, proceed to Copenhagen.
  11. May 13, 2007 #10
    Do you mean Stockholm?

    Perhaps we do observe matter-antimatter anhilation as very high energy gamma rays.

    I'm kinda curious as to why ultra-high cosmic rays could not be the result of matter-antimatter anhilation, since presumably that would also result in high energy gamma rays.

    Perhaps there is a mechanism that keeps matter and antimatter seperate.

    I do know that there are attempts to create significant quantities of antimatter-hydrogen to test their gravitational properites.

    Perhaps there is an unknown mechanism that keeps them from coming together, or
    perhaps it was sheer luck that moments after the big bang, half of the matter was on one side, the other half on the other side, and with early inflation they separated.

    Perhaps there is parity in loop quantum gravity which causes matter to be more likely to be created than antimatter.
  12. May 13, 2007 #11


    User Avatar

    I thought that the scientists had killed the big bang and replaced it with a "bounce"
    and that the inflation had been replaced with "re-heating"
    I'm waiting for them to annouce a new mechanism for expansion.:smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook